U.S. Department of the Interior 
Geological Survey
Seismic-reflection and echo-sounder data from R/V FARNELLA cruise 
FRNL85-4 in the Puerto Rico and U.S. Virgin Islands 
Exclusive Economic Zone
by Kathryn M. Scanlon1
Open-File Report 90-38
This report is preliminary and has not been reviewed for conformity with 
U.S. Geological Survey editorial standards. Any use of trade names is for 
descriptive purposes only and does not imply endorsement by the U.S. 
Geological Survey.
1989 
1 USGS, Woods Hole, MA
Seismic-reflection and echo-sounder data from R/V FARNELLA cruise FRNL85-4 
in the Puerto Rico and U.S. Virgin Islands EEZ
by
Kathryn M. Scanlon
Between November 4th and December 3rd, 1985, the U.S. Geological Survey 
in cooperation with Great Britain's Institute of Oceanographic Sciences 
collected over 9,500 line kilometers of seismic-reflection and echo- 
sounder profile data in the Exclusive Economic Zone of Puerto Rico and the 
U.S. Virgin Islands (Fig. 1). 
North of the islands, the survey covers 
parts of the Greater Antilles Outer Ridge and the Puerto Rico Trench; 
south of the islands, it covers parts of the Muertos Trough and the 
Venezuelan Basin. 
Data were also collected on the insular slopes north 
and south of the islands in water depths greater than about 500 meters 
(m).
The work was conducted aboard the research vessel FARNELLA on cruise 
FRNL85-4. 
Line spacing was about 37 km in the deep areas (ie., north of 
about 19°N and south of about 17.5°N) and as close as 10 km in the 
shallower areas near the islands (i.e., between about 17.5°N and 19°N). 
GLORIA long-range sidescan-sonar data were collected simultaneously with 
the seismic-reflection data and are discussed elsewhere (EEZ-SCAN 85 
Scientific Staff, 1987). Magnetic data and digitized bathymetric data are 
also available from all of the FRNL85-4 tracklines shown in Figure 1
(Scanlon, 1986).
Navigational control was maintained by an integrated navigation system 
using mainly transit satellites, gyro compass, and doppler speed log. 
Global Positioning System (GPS) fixes were also used during the few hours 
each day when at least three GPS satellites were within range.
The seismic-reflection data were collected using a single 80-or 160- 
in3 airgun as the seismic source and a two-channel hydrophone receiver 
with 48 elements in each of two active sections. 
The airgun was fired 
every 15 seconds using air compressed to 1500 pounds per square inch. The 
signals from the two channels were summed together and recorded on flatbed 
paper recorders at 5- and 10-second sweeps. 
The signal was filtered 
between 20 and 200 Hz. 
Data quality is good and has a maximum subbottom 
penetration of about 1 second.
Echo-sounder data were collected using both 3.5 and 10 kHz systems 
simultaneously along all tracklines (Fig. 1). 
The 3.5 kHz data were 
recorded on a flatbed paper recorder at a 2-second sweep. 
The 10kHz data 
were recorded on a wet-paper recorder at a 1-second sweep. 
Data quality 
varies from poor to excellent, the lowest quality data being from the 
steepest parts of the insular slopes.
The original seismic records may be examined at the U.S. Geological 
Survey, Woods Hole, MA 02543. 
Microfilm copies of these data can be 
purchased only from the National Geophysical Data Center, 325 Broadway, 
Boulder, CO 80303, telephone (303) 497-6345.
REFERENCES
EEZ-SCAN 85 Scientific Staff, 1987, Atlas of the U.S. Exclusive 
Economic Zone, Eastern Caribbean: U.S. Geological Survey 
Miscellaneous Investigations Series, I-1864B, 58 p., scale 
1:500,000.
Scanlon, K.M., 1986, Magnetic and Bathymetric Data from R/V FARNELIA 
Cruise FRNL 85-4 in the Puerto Rico and U.S. Virgin Islands EEZ, U.S 
Geological Survey Open-File Report 86-399, 2 p.
Figure 1 
Map showing the research vessel FARNELLA's tracklines (fine 
lines) within the U.S. Exclusive Economic Zone boundary (heavy line) of 
Puerto Rico and the U.S. Virgin Islands along which the seismic-reflection 
and echo-sounder data were collected.
22«
68e
EEZ BOUNDARY
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FARNELLA
1985
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USGS/IOS GLORIA SURVEY
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